Jews are well accustomed to the
fact that our religious calendar marches to a completely different rhythm from
the one that is in common use in the surrounding society. There is however a
conspicuous exception to that pattern: The day on which we begin to pray for
rain in our daily prayers (introducing the Hebrew formula "Ten tal
umatar") is defined in the Siddur by a date in the "civil" calendar,
the 4th (or sometimes the 5th) of December.

The origins of this anomaly go back to ancient times, when the Rabbis of
Babylonia decreed that rain should not be requested prior to the sixtieth day
after the Autumnal Equinox. The significance of this date is not explained in
the Talmud, and some scholars have suggested that for the Babylonian farmers
rainfall was considered a nuisance before the conclusion of the date-harvest.
Whatever the reason, it is clear that the equinox, as a phase in the cycle of
the sun, is most conveniently calculated by the civil calendar, which is a
solar one.

In the course of the Middle Ages the Babylonian practice came to be
accepted--though not without a struggle--by all Jewish communities outside the
Holy Land. Israel itself follows a different, earlier date, defined according
to the Jewish calendar (the 7th of Heshvan).

Initially many Diaspora communities followed the Israeli custom, but
eventually the powerful Babylonian Rabbinate succeeded in asserting its
authority as the supreme authority for religious practice.

Thus, as an eminent contemporary halakhist has observed, normative practice
has rejected the more reasonable precedents of praying for rain either when it
is beneficial for our own climate, or when it is required in the Holy Land--in
favour of the unlikely option of linking it to the climate of Iraq (the current
inhabitant of the land that was formerly called Babylonia).

But the peculiarity of the situation does not end there. The Autumnal Equinox
actually occurs on the 22nd of September, so that the sixtieth day following
should come out on November 20, not December 4!

The discrepancy originates in the methods that we employ for calculating the
solar year. The Talmud assumes that a year consists of precisely 365
1/4 days and halakhic practice bases its calculations on that
premise.

The calculation is very close, but it is not fully accurate, since an
astronomical year falls eleven minutes and fourteen seconds behind that
estimate. The margin is admittedly a tiny one, but when stretched across the
centuries of Jewish history the minutes begin to add up. Every 128 years the
Jewish reckoning pulls a full day ahead of the astronomical equinox.

The Catholic Church, aware that their traditional Julian calendar (based on
the same assumptions as the Talmud's) had lost touch with the facts of nature,
corrected the situation through the introduction of the Gregorian calendar in
1582, which involved turning the clocks ahead eleven days to adjust for the
discrepancy! The Gregorian calendar cleverly regulates the frequency of
leap-years in order to keep the equinoxes in astronomic proportion. It has now
become the accepted standard for most of the world.

Because the Jewish world has never introduced an equivalent adjustment, the
cumulative error over the centuries now amounts to fifteen full days.

And the gap will continue to widen. Even as Siddurim published a
century ago instruct the worshippers to begin reciting "Ten tal umatar"
on December 3 or 4, so in the year 2100 will the dates shift to Dec. 5 or
6--gaining three days every four hundred years.

If left uncorrected this will lead to some bizarre consequences, as the season
for reciting "Ten tal umatar" keeps shrinking. Eventually it will
advance all the way to Passover, which marks the termination of the rainy
season, and will not be recited at all. Although this is a mathematical
inevitability, don't hold your breaths. It is not scheduled to happen yet for
another 35,000 years.

As often happens, the halakhic world tends to prefer its own traditional rules
and definitions over ones that issue from the outside world. Some Rabbis have
taken note of the problem, but are reluctant to tamper with traditions. Almost
none have discerned any cause for alarm.

After all, they argue, we live in faith that the Messiah will appear at any
moment. Surely he will arrive before matters get out of hand, so why don't we
just wait and let him deal with the problem!